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Vertical Loops

If the soil conditions are not conducive to trenching, then a vertical system may be the choice. Vertical systems are used where land area is limited, where the soil is too rocky for an economic horizontal system, and for commercial or educational facilities. Spacing vertical boreholes can be in any variety of ways - lines, squares, rectangles, grids - depending on available land areas and system borehole requirements.

The ground heat exchanger may be either series or parallel piping. Each has both advantages and disadvantages.

Series SystemAdvantages:

Single flow path and pipe size

Slightly higher thermal performance per foot of pipe since a larger diameter pipe is required.

Disadvantages:

Larger water or antifreeze volume of larger pipe

Higher price per foot of piping material

Increased installed labor cost

Limited length due to fluid pressure drop and pumping costs.

Parallel System Fabricated from smaller diameter pipe (which is generally less costly), special care must be taken in flushing to get all the air out of the piping loop.

Advantages:

Lower cost pipe

Less antifreeze required

Lower installation labor cost

Disadvantages:

Special attention to assure air removal

Attention to balanced flow, within plus or minus 5 percent, in each parallel path is required.

Major Components The major components of these heat exchangers are:

Supply and return headers of larger pipe to minimize the pressure loss down the length of the pipe run from the equipment to the vertical loop.

Loops extending from the supply header down the borehole and back, connected to the return header

Reverse return or compact headers to allow each loop to have approximately the same flow